Why does fluorine have a higher electronegativity than iodine, even though they are both halogens?

Fluorine has a higher electronegativity than iodine because it is much smaller and its valence electrons are closer to the nucleus. This allows fluorine to exert a stronger pull on shared electrons in a bond, making it more electronegative. Iodine's valence electrons are further away from the nucleus and experience more shielding, reducing its electronegativity.